ABSTRACTCu‐enriched pig‐mannre slurry was applied to grassland at two rates, 5000 and 10,000 gal/ac (56,000 and 112,000 I/ha), on three occasions, supplying a total of 5.4 Ib/ac (6.1 kg/ha) and 10.8 Ib/ac (12.2 kg/ha) Cu, respectively. At the higher rate, soil Cu extractable with EDTA increased from 24 ppm to 7.3 ppm Cu in samples taken to a depth of 3 in. (7.5 cm) and Cu in herhage DM increased from 9.1 ppm to 21.2 ppm Cu (mean of 5 cuts). Much of the additional Cu in the herhage was thought to be derived from external contamination. In other tests, leafy herbage sampled a few hours after applying slurry contained 338 ppm Cu in the DM.Samples of soil and herbage were taken in 1969, 1970 and 1971 from farm grassland that had received Cu‐enriched pig‐manure slurry each year; levels of Cu increased in the soil, Cu levels in herbage were variable and appeared to be affected by the rate of grass growth.The evidence suggests that there is at present littie risk of Cu toxicity following applications of Cu‐enriched pig‐manure slurry; the greatest risk to susceptible stock would appear to be by ingesting either grazed or conserved herbage contaminated with slurry. To avoid possible hazards from a build‐up of Cu in the soil, a maximum annual application of ahout 8.5 Ib/ac (9.5 kg/ha) Cu is suggested until more is known on the availability of Cu in slurry to cr